Selves and edwaed cunningham



(No maar.) f

JL LEWIS 8v F. A. BROWN.

. MARINBRSCOMBASS. l 10.247,505, Patented Sept. 27,1881.

UNITED STATES PATENT OFFICE.

JOHN LEWIS AND FREDERICK A. BROWN, OF BOSTON, ASSIGNORS TO THEM- SELVES AND EDWARD CUNNINGHAM, OF EAST MILTON, MASS.

MARINERS COMPASS.

SPECIFICATION forming part of Letters Patent No. 247,505, dated September 27,1881.

Application filed June 27, 1881. (No modem To all whom it may concern Be it known that we, JOHN LEWIS and FREDERICK AUGUSTUS BROWN, of Boston, of the county of Suffolk and State ot' Massachusetts, have invented a new and useful Improvement in Mariner-s Com pasess; and we do hereby declare the same to be described in the following specication and represented in the accompanying drawings, of which- Fi ure l is a top view, Fig. 2 a bottom view, and ig. 3 a transverse section, of a compass card and float provided with our invention, which has special reference to the cards and floats of what are termed liquid compasses.77

We have found in practice that a floatable compass-card and its magnetic needle, having a 'series of sets of U-shaped magnets arranged on the lower surface of the ioat or a plate fixed thereto) and at or near the periphery of the iioat, though capable of eftectually resisting local attraction, is liable at times to be somewhat sluggish in its movements, and not always to be depended on for accurate po.- larity, such being due to the friction and resistance resulting from the edges of the needle, the magnets, and the oat in moving in the fluid in which they may be placed. To obviate this difficulty we employ, with the oat and its needle and sets of U-magnets, an auxiliary magnetic needle, which we extend across the oat, or in or over its upper side or part, or between such and the card when the latter is used.

In case of the divisions and points of the card being marked directly on the upper surface of the iioat, the separate card or disk having such divisions or marks upon it would not be needed.

We have found that the above arrangement of the auxiliary needle is better than to place ,it immediately underneath the oat and in the plane of the U-magnets, or to increase the depth of the main needle, in order to increase its magnetic force, for in these latter cases there seems to be produced, from some unknown cause, an impediment to the proper action of the magnet to overcome local attrac ability of the sets of U-magnets to resist local attraction is 4not impaired. Besides, by making the card with a central opening and extending the auxiliary magnetic needle across sucli diametrically in the meridian-line of the card, the needle serves as a guide for the mariner readily to distinguish the north and south points of the meridian-line from their nauking-points.

In the drawings, A denotes the float; B, the main magnetic needle, O C, 8vo., the series of of sets of U-magnets; D, the auxiliary magnetic needle, and E, the card or disk marked with the points of the compass and having a circular opening, a, at its center, all being ar ranged as set forth.

A hollow conical standard, l, open at its lower end and erected on the bottom of the float, serves to support the pivotal bearing or step of the oat, which may be screwed or fixed into such standard and go through the auxiliary needle at its middle, and aid, with the standard, in holding such needle in place.

We prefer to have the compass-card made of glass with a colored vitrified surface, such surface in the spaces between the points be ing removed by fluoric acid, so as to form the points from such colored surface. In such case the glass card is not liable to be injured by the alcohol or fluid generallyT employed in the bowl of the compass.

We claim as our invention as follows, viz:

l. The combination of the iioat and its magnetic needle and sets of U-magnets arranged below or against the bottom of such float with the auxiliary magnetic needle disposed above the float or applied to the upper part or top thereof, all being substantially as set forth.

" 2. The combination of the open compass= card, the oat, the main and auxiliary mag netic needles, and the sets of Uimagnets, ar ranged and combined substantially as described and represented.

3. The combination'of the float and its cen tral tubular standard with the main and auxmagnets, arranged and adapted substantially iliary magnetic needles and the sets of U-magrns shown and described.

nets arranged with such float and standard, JOHN LEWIS.

substantially as seb forth. FREDERICK AUGUSTUS BROWN.

el. The combination ofthe oat, the tubular Witnesses:

standarchthe open compass-card, the main and R. H. EDDY,

auxiliary magnetic needles, and the sets 0f U- E. B. PRATT. 

